This invention relates in general to cushions and more particularly to cushions formed from a resilient material such as a foamed polymer.
The typical cushion used for supporting the body in a prone position or a seated position, such as a mattress, a seat cushion, or a padded back rest, acts much like a conventional coil spring in that the restoring force exerted against a body which deforms it is generally proportional to the extent of the deformation. Thus, in the case of a mattress, the hip region might protrude further into the mattress than the adjoining waist or thigh regions, and as a consequence the supporting pressure exerted by the mattress would be greater at the hip than at the thigh or the waist. From both the standpoint of comfort and health it is not desirable to concentrate the supporting force at any particular region of the body.
With individuals who are confined to bed for extended periods of time it is most important to avoid prolonged concentration of the supporting force on particular regions of the body. Indeed, any skin area to which sustained pressure is applied experiences a reduction in the flow of blood and as a consequence this particular skin area does not receive sufficient oxygen or nutrients. Decubities ulcers may develop as a result of these deficiencies, and these ulcers can be quite uncomfortable as well as life-threatening. Individuals who have become immobile or sensitive to touch require a cushion that does not interfere with blood flow at sensitive skin areas. Suspension forces that are distributed in a hydrostatic-like manner cause the least interference with blood flow and are least likely to produce cell neurosis.
Individuals who are immobile often have difficient lymph systems, and it is one's lymph system that controls the onset or extent of edema, which in itself is a debilitating condition. However, edema may be minimized at the contact site on the skin area and its debilitating effects likewise minimized by the application of a hydrostatic-like counter pressure to the body.
Thus, it is desirable to have a body supporting cushion, whether it be in the form of a mattress, a seat cushion, or a back rest, which applies a generally uniform supporting pressure, that is a hydrostatic-like counter pressure, over the skin area in contact with it. Heretofore, cushions have been developed which approach this end, but these cushions rely on entrapped fluids, such as air or water, and are therefore complicated in construction and expensive to manufacture. Moreover, these cushions, for the most part, do not allow air to circulate around the supported area, and the absence of air is also harmful to the skin.
Conventional cushions of the type formed from resilient foam materials, such as expanded polyurethane, on the other hand, are simple and inexpensive to manufacture, but they do not exert uniform supporting pressure on the supported region of the body. Instead, they behave much in the same manner as a conventional spring mattress.